The invention relates to a device for the preparation of plastics material, in particular thermoplastic plastics material, with a receiving container for the material to be treated, the interior of the receiving container having tools provided therein which are arranged on a carrier disc and which are driven by a shaft inserted into the interior for rotation about the, in particular vertical, axis of the shaft, and with at least one screw for removing the material out of the receiving container, the screw housing having a feed opening which is connected with respect to flow to a discharge opening in the receiving container, which discharge opening is situated at a lower level than the carrier disc and the tools carried by it, and further moved tools which convey the material into the discharge opening being provided in the receiving container below the carrier disc.
device of this type, known from WO 00/74912 A1, has proved highly successful for the preparation of plastics material, in particular thermoplastic plastics material, but it has been found that a blocking-in of the volatile substances released by the treated material occasionally occurs in the space below the carrier disc. It is not always possible for these volatile substances to escape upwards through the annular gap existing between the edge of the carrier disc and the inner wall of the receiving container, particularly since the material to be treated passes downwards from above through the annular gap. It is particularly undesirable if the volatile substances are removed with the treated material out of the receiving container and arrive in the extruder which is attached directly or indirectly to the receiving container, since there is then a risk that inclusions of gas of various types will be present in the extruded material, and this substantially reduces the quality of the material contained at the outlet of the extruder. This risk cannot be entirely eliminated even by a degassing device generally provided in the extruder. In addition, volatile substances of this type cannot generally be prevented from the beginning, since they are water vapor, separation products of the material to be treated, gaseous or evaporated portions of coolant, etc. In particular, in the case of moist plastics material introduced into the receiving container, these volatile substances can be substantial.